The invention relates to an ossicular prosthesis which replaces or bridges at least one member or parts of a member of the ossicular chain, wherein the ossicular prosthesis comprises, at its one end, a first fastening element in the form of a head plate which is intended to mechanically rest against the tympanic membrane and/or against the malleus handle and, at its other end, a second fastening element for the mechanical connection to one member or parts of a member of the ossicular chain, or to the inner ear, and a connecting element which connects the two fastening elements to one another in a sound-conducting manner along a longitudinal axis, and wherein the head plate comprises a radially inner coupling region situated centrally with respect to the longitudinal axis for the mechanical coupling of the head plate to the connecting element, and multiple bridging elements extending outwardly from the central coupling region, radially away from the longitudinal axis, each of which is connected to the central coupling region via a radially inner end region and transitions into a radially outer, free end section. A device of this type is known from DE 10 2007 013 708 B3.
Ossicular prostheses are used in cases in which the ossicles of the human middle ear are missing or damaged, either entirely or partially, in order to conduct sound from the tympanic membrane to the inner ear. The ossicular prosthesis has two ends in this case, wherein, depending on the specific conditions, one end of the ossicular prosthesis rests against the tympanic membrane or against the malleus handle, for example by means of a head plate, and the other end of the ossicular prosthesis is fastened, for example, to the stapes of the human ossicular chain, or is inserted directly into the inner ear. In the known ossicular prostheses, sound conduction between the tympanic membrane and the inner ear is often limited because the ossicular prostheses cannot fully replace the natural anatomical formations of the ossicular chain.
After the prosthesis has been surgically implanted in the middle ear and the tympanic membrane has been closed, the so-called recovery phase begins. Scars form during this period, and they produce unforeseeable forces which can cause the prosthesis to move out of its local position. When there is a stiff connection between the head plate and the shaft, increased pressure peaks can result between the edge of the head plate and the tympanic membrane or the graft between the tympanic membrane and the head plate. These pressure peaks can be so high that penetration or extrusion through the tympanic membrane would result. For this reason, it is very helpful when the prosthesis has a certain postoperative mobility, so that the head plate can automatically adapt, postoperatively, to the position of the tympanic membrane.
Since, in addition, the unique anatomical features of the ear, such as the position, shape and size of the stapes, incus, hammer and tympanic membrane, vary, it is highly advantageous when ossicular prostheses do not have a rigid configuration, but rather have a certain amount of flexibility or variability.
In order to attain this level of flexibility/variability, it is known to use various fastening and coupling devices for ossicles, which have elastic parts and/or articulations. Such an articulated connection between a fastening element, which can be installed on the stapes footplate, and the elongate shaft is described, for example, in EP 1 181 907 B1, and is offered by the applicant under the trade mark “Ball-Joint”.
A further complication that occasionally arises is caused by inadequate ventilation of the middle ear space and the associated inflammation, tumor formation, adhesions in the region of the tympanic membrane, and stiffening thereof. When the eustachian tube malfunctions, for example, underpressure may form in the middle ear, which can cause the tympanic membrane to protrude (or retract), thereby resulting in adhesion with the stapes, for example. In order to counteract this, and in order to enable postoperative movements of the tympanic membrane to be followed, the head plates of known ossicular prostheses are designed to be tiltable relative to the connecting element which connects the head plate to the second fastening element and is usually designed as an elongate shaft. A head plate of this type, which is rigid yet tiltable relative to the connecting element, is described, inter alia, in US 2004/0162614 A1, in the article M. W. YUNG, Ph.D., F. R. C. S., D. L. O., C. BREWIS, F. R. C. S., “A comparison of the user-friendliness of hydroxyapatite and titanium ossicular prostheses”, The Journal of Laryngology & Otology, February 2002, Vol. 116, pp. 97-102, or, for example, in US 2006/0271190 A1.
DE 20 2005 003 782 U1 describes an ossicular prosthesis, in which the head plate comprises an integrated ball joint which is connected to the connecting shaft of the two fastening elements.
The disadvantage of these known ossicular prostheses, however, is that, due to the rigid tilting of the head plate that occurs in the event of local medial movements of the tympanic membrane, the opposite side of the head plate is simultaneously moved laterally outward, thereby generating pressure peaks on the tympanic membrane.
Finally, DE 10 2007 013 708 B3, which was cited at the outset, discloses an ossicular prosthesis of the type in question, which comprises a head plate having a highly flexible configuration, in the case of which the advantages of the prosthesis according to the aforementioned document DE 20 2005 003 782 U1, on the one hand, and, on the other hand, the advantages of the prostheses described in US 2004/0162614 A1 and US 2006/0271190 A1 are retained, wherein, however, the shared disadvantages of a rigid tilting of the head plate are avoided. One problem associated with the ossicular prosthesis according to DE 10 2007 013 708 B3, however, is its insertion into the middle ear of the patient, because the head plate protrudes laterally outward to a considerable extent, in particular in the radial direction relative to its longitudinal axis, and can only be surgically inserted through the tympanic membrane region into the middle ear by means of a large artificial opening. This large opening then also has a more difficult time healing postoperatively, of course, and also leaves correspondingly large scars.